1. Field of the Invention
The present invention relates generally to Virtual Execution Environment technology and, more particularly, to a method and system for generation and management of incremental backups using bitmaps of file system snapshots.
2. Background Art
In the past decade, capabilities of computer systems have increased significantly. Computer systems process large volumes of data, which is changed or updated constantly. In order to track changes of data, files located on a system Hard Disk Drive (HDD) are usually copied, and a system data backup based on these files is created. This enables a user to access previous versions of files, as well as to protect data from possible system failure.
Typically, data backups performed on a physical machine do not require saving of any system configuration parameters, because the structure of the physical machine remains the same. Thus, making the snapshot of data of the HDD is sufficient for generating a backup. Conventional data snapshot is generated by an Operating System (OS) of the physical machine.
The industry trend of virtualization and isolation of computer system resources makes the task of generating backups more complex. A Virtual Execution Environment (VEE), such as, for example, a Virtual Machine (VM) or a Virtual Private Server (VPS) is a type of an isolated VEE that runs on the same physical machine simultaneously.
Virtualization allows running a number of VEEs on the same physical machine or processor. Thus, scheduling and controlling efficient backups of data among numerous VEEs becomes even more crucial. Furthermore, configuration of each of the VEEs can be changed by a user. Thus, saving snapshots of all previous states of a particular VEE into a backup is critical.
Typically, data backups are performed by system administrators according to backup schedules. With VEEs, it is important to allow users to perform backups at any time, when the state of the VEE is about to change. A snapshot used for a backup of a VEE typically includes a bitmap of a virtual file system. The bitmaps are normally parts of backups generated based on disk image (i.e., block level backups).
Generating a bitmap of a snapshot of an empty VEE file system or a snapshot of VEE file system containing small volume of data can be done relatively fast, in a matter of a few seconds. However, generating a bitmap of a snapshot of VEE file system populated with a lot of data takes a long time, which can be in the hundreds of seconds. During this time, all data contained in the VEE file system is automatically frozen and is not accessible to users. Conventionally, this can involve freezing an entire disk drive. Obviously, this is inconvenient for the users and makes the task of scheduling and generation of backups problematic for system administrators. Such long delays may also be a violation of the Service Level Agreement.
Accordingly, there is a need for a system and a method for fast and efficient generation of bitmaps of snapshots of VEE file system without freezing the file system for the duration of the backup process.